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Team:IIT Delhi/Project
From 2014.igem.org
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Origin of Our Project
- ✔ In today’s modern world, greenhouse gases such as NOx and SOx pose a major global issue that needs to be addressed. These oxides also increase the oxidizing capacity of the atmosphere which are responsible for the photochemical production of ozone in the lower layers of the atmosphere which has detrimental effects. Sulfur Oxides (SOx) are the main precursors of air pollution which is a deteriorating problem as well. Producing acid rain and acidified soils, Sulfur Oxides not only result in respiratory problems such as asthma and pneumonia, but also destroy farm crops, buildings and environment, causing loss of millions of dollars every year.
- ✔ Both these gases also have detrimental effects on the environment and our team plans to combat this catastrophic effect by reducing the amount of the NOx and SOx gases ejected through the exhaust vents. For this we have engineered nrfA gene (codes for nitrite reductase) in E.Coli to convert NOx to NH3 (Clarke et al;2008) and for SOx reduction we will incorporate cysI(sulfite reductase) that converts SO2 to H2S (Growth Yields and Growth Rates of. Desulfovibrio vulgaris (Marburg) growing on Hydrogen plus Sulfate and Hydrogen plus Thiosulfate as the Sole Energy Sources, Arch. Microbiol. 117, 209-214 [1978]) and sqr (sulfide quinone reductase) to convert H2S to S. In order to realize the whole sulfur metabolism pathway, we use several bioinformatics web sites such as KEGG and NCBI. We anticipate that the use of genetically engineered bacterium would subside the efficiency of existing chemical methods.
Milestones of the project
- ✔ We engineered E.Coli for Nitric Oxide (NOx) and Sulfur Oxides (SOx, SO2 ) reduction.
- • Engineered a plasmid that expresses the nitrite reductase enzyme (nrfA) under a constitutive promoter for high and unregulated rate of expression. We obtained the nrfA coding biobrick from previous iGEM project of Team KENT. The new biobrick we made expresses nrfA which would convert the NOx to ammonia.
- • Engineereed a plasmid that would express the Sulfite reductase (cysI or Dsr) and Sulfide-Quinone reductase (Sqr) under a constitutive promoter. CystI and Dsr were cloned from Pseudomonas Aeruginosa and Desulfovibrio Desulfuricans respectively. Sqr was obtained from Synechococcus (SP. PCC 7942). Sulfite reductase converts SO-3 to H2S and sulfide-quinone reductase convert S-2 to S.
- • To test the working of the engineered bacteria for the reduction of the NOx and SOx gases we decided to design a prototype model of the reactor.
- •Although we were unable to design a prototype, but we have done design calculations and made a solidworks model for the reduction of NOx and SOx from the exhaust gases.
Work plan (methodology/experimental design that we have accomplished to achieve our aim)
- (a) Engineering the E.coli
- ● NOx removal:We tackled the nitric oxide produced during the combustion processes by using the nitrite reductase enzyme NrfA of E. coli. We engineered a plasmid that expresses the nitrite reductase enzyme NrfA under the control of a constitutive promoter so that the promoter is active independent of transcription factors, and is "on" by default. nrfA will be expressed in excess and will convert the NO to ammonia.
- ● SOx removal: Sulfur Oxides (SOx, SO2) are the main precursors of air pollution which is a serious problem now a days. Apart from producing acid rain and acidified soils, Sulfur Oxides also cause breathing problems such as asthma, pneumonia and destroy farm crops, buildings and environment as well, causing millions in loss each year. Our plan is to genetically engineer E.coli by cloning CysI gene into E.coli and use this bacteria to remove SO2 from our environment. Also, this bacteria produces H2S, which is a substrate for Sulfide-Quinone Reductase (sqr). This H2S will get converted to Sulphur.
- (b) Designing tabletop model- The hypothetical prototype has the following components
- 1.A small Heat Exchanger: Since the temperature of the exhaust gases would be very high for our engineered bacterium to work, we have decided to use an heat exchanger for reducing the temp of the exhaust gases.
- 2. Bioreactor: It is the most important part of the design where the reduction of the harmful gases takes places. The genetically engineered E.Coli is immobilized in the bioreactor and responsible for all the reduction of gases inside the reactor. The gases pass from the bottom and the medium is sprayed at a very slow rate from the top of the reactor. The immobilization material is polymeric material with a positive zeta potential. The prototype design is a proof of the concept, which can undergo various changes on the basis of the requirements of the industry. The concept of reduction of harmful gases using genetically engineered bacteria can be used in automobiles, thermal power stations and various other industries. The size of the device needs to be manipulated according to the industrial requirement.
- 3. A medium tank: This includes a solution having all the nutritional requirement of the bacteria. Thus it will contain a minimal medium required by the bacteria for its growth.
The relevance and expected outcome of the proposed study
- ✔ Our project integrates biochemical engineering and synthetic biology.Synthetic biology is the revolutionary science of the future. Although the organisms reducing the harmful nitrogen and Sulfur oxides exist in nature, the reason of using genetically modified bacteria is to increase the efficiency and the rate of reduction of the oxides by the bacteria. Our proposed biological system has significant benefits over current removal methods. It would be substantially cheaper to use, as it would not need high temperatures required for other methods, nor would it need the costly catalysts used in Selective catalyst reaction (SCR).
- ✔ The absence of SCR catalysts from our system would also mean that it would lack the potential toxicity that can arise from metal by-products of catalyst degradation. In addition, being operated by genetically modified bacteria, our system could be more flexibly implemented, since provided optimal growth conditions, they may be operated on a variety of production levels and in a variety of mechanical systems. For example, many waste water purification systems already use batches of bacteria that degrade a significant proportion of pollutants present in waste water, and so our modified bacteria could be added into this batch to improve NOx clearance.Our project aims at reducing the emission of harmful Sulfur and nitrogen oxides by industries. These oxides are harmful as they are the main reason of the present day acid rain which leads to a number of problems ranging from deterioration of the fertility of agricultural lands to polluting the water bodies.
Scope of application indicating anticipated product and processes
- ✔Applicability to the Indian environment and Benefits to Indian society, especially economically weaker segments: India is a tropical country and the release of greenhouse gases adds to the elevation of the temperature. A lot of research is being carried out and high cost equipment are being used to reduce the amount of greenhouse emissions. Our project aims to be an economical and efficient substitute for reducing global warming. According to WHO report, about 15-20 million people in India are asthmatic and it’s high time that the level of gases such as NOx and SOx in the atmosphere is controlled. Apart from this, agriculture is the mainstay of the Indian economy and hampering of agricultural lands by acid rain will cause a major loss to the nation. Our model will help in resolving all these issues by converting harmful greenhouse gases that affects our health, agriculture and the economy, to non-harmful compounds and also useful compounds.
- ✔ Scalability-The ability of the innovation to export to the real world and change it. Pragmatism is highly encouraged. Scalability is defined as the ability of a system or a process to handle a growing amount of work in a capable manner or its ability to be enlarged to accommodate that growth. The utility of our model is manifold. It varies from installing it in a small compartment in an automobile to something as large as the chimney of a thermal power plant. The handiness of our model is derived from the fact that all of the sub-components work independent of each other and hence can be easily detached and replaced. For example, the medium can be replenished at regular intervals by detaching the medium container. Similarly we can replace the reaction chamber and wash out the dead bacteria.
- Our project is scalable in various dimensions: Firstly it has load scalability i.e. we can expand and contract our inputs depending on the required output. For example if our project has to be installed in the chimney of a factory or a thermal power plant, where the load of input gases is very high, we can increase the size of our reaction column or increase the flow rate of the medium i.e. scale up our model to perform in proportion to the input load without loss of efficiency. On the other hand, if we intend to use our model to reduce the concentration of NOx and SOx in the exhaust gases of an automobile we can very efficiently scale it down. We can again modify the size of the reaction column or the flow rate of the medium since all these factors are under our control.
Outreach: Industrial Visits and Discussions
- ✔ Our Team went to NTPC (National Thermal Power Corporation) Plant,Dadri, New Delhi India India. We visited their plant and discussed about our project, here are some pictures of our visit:
